Carriers are utilized in many different axle and suspension configurations. A carrier includes a pinion gear that receives driving input from a power source such as an engine or electric motor. The pinion gear drives a ring gear, which is coupled to a differential. The differential allows speed differentiation between two different driving outputs. The driving outputs are configured to drive laterally spaced vehicle wheels.
The carrier includes a carrier housing that houses and protects the pinion gear, ring gear, and differential within an internal cavity. The carrier can be utilized with different types of axles and suspensions. For example, the carrier can be utilized in a rigid axle configuration with leaf or air spring suspensions where the carrier housing is formed as part of a rigid axle housing that extends between the laterally spaced vehicle wheels. In this configuration the carrier housing comprises an open bowl portion centrally formed within the rigid axle housing that receives carrier gear components, and which is enclosed by a cover portion.
The carrier can also be utilized as part of an axle that is configured to be mounted to a vehicle with an independent suspension. In this type of configuration, the carrier is mounted to a sub-frame unit that is positioned between laterally spaced wheel ends. The sub-frame unit is attached to a vehicle frame or chassis. Upper and lower control arms connect each wheel end to the sub-frame unit such that each wheel end can move independently from the other wheel end within a wheel jounce travel range.
Certain vehicle applications require large amounts of wheel jounce travel. Wheel jounce is defined as vertical movement of a wheel or axle relative to a vehicle reference frame. Jounce is considered positive for compressive movement, i.e. movement of the wheel upward relative to a vehicle body. In order to accommodate a large amount of wheel jounce travel, the length of the upper and lower control arms needs to be increased. However, the wheel ends often cannot simply be spaced further apart from each other to accommodate this increased control arm length. This is because there are maximum overall axle width requirements that cannot be exceeded if the vehicle is to travel on city streets and highways. Thus, the packaging space taken up by the carrier becomes critical to maintaining maximum axle width in combination with increased wheel jounce travel ranges.
Traditional carrier construction makes it very difficult to provide a narrow width carrier that could be used with an independent suspension as described above. If high reduction ratios are required for a vehicle application, the ring gear must be appropriately sized to provide the desired power transmission. In some applications, the ring gear must have a diameter that is greater than 11 inches. Further, in traditional carrier configurations, carrier components can only be located in certain positions within the carrier housing such that other components can be assembled into the carrier housing.
Specifically, the differential includes a plain case half supported by a plain side bearing and a flange case half supported by a flange side bearing. The plain side bearing cannot be located inboard of a maximum outer diameter of a head of the pinion gear because the pinion gear would not be able to assemble into the carrier.
Thus, there is a need for a new carrier system architecture that allows the overall width of a carrier to be reduced compared to traditional carrier configurations, but still provides desired power transmission and suspension characteristics.